The present invention relates to a method and an apparatus for treating blood in various ways such as removing impurities and deleterious matter, and replacement of specific components.
For the treatment of various diseases, blood is treated in various ways, among which the following are conventionally known: a method in which plasma is separated from a blood sample and loaded on an adsorption column to remove the unwanted or deleterious matter by adsorption; plasma exchange in which the separated plasma is replaced by a replenishing fluid; double filtration for removing higher molecular weight components of the plasma; and artificial dialysis in which the blood sample is brought into contact with a semipermeable membrane.
These blood treating methods are implemented with an apparatus of blood treatment which generally comprises a cascade connection of a collection circuit for withdrawing a blood sample by means of a blood pump, a treating circuit for performing specified treatment on the blood sample and a return circuit through which the treated blood sample is returned to the patient. In addition, a heparin pump, a filter, a blood warmer, an air bubble detector, as well as a plurality of pressure gauges and clamp valves are provided at appropriate sites in the respective circuits. If the apparatus is a type that treats a separated plasma component of blood, a plasma separator, a plasma pump, a blood leak detector, an adsorber or a secondary filter and the like are also provided in the treatment circuit.
The apparatus of blood treatment having the construction described above is usually provided with control means for controlling the driving of the pumps and the opening/closing of the clamp valves such that the blood treatment can be accomplished by automated operation of the apparatus.
If any abnormality occurs to the pressures in the circuits or to devices in the apparatus of blood treatment during its use, the operation of the pumps has to be controlled in an appropriate way depending on the nature of the abnormality. According to Examined Japanese Patent Publications Nos. 28981/1990 and 50304/1993, if the blood withdrawing portion of an apparatus of blood treatment becomes constricted during treatment to produce a great negative pressure in the primary flow channel to the first pump, a further increase in the negative pressure can be avoided by reducing the rotating speeds of the first and second pumps while keeping the ratio between their flow rates constant.
This method is capable of dealing with the increase in negative pressure that occurs in the primary flow channel to the first pump on account of the constriction of the blood withdrawing portion of the apparatus of blood treatment. However, neither of the patents mentioned above discloses a technique for controlling the pumps when other abnormal events occur and while the operation restores the normal state.